This invention relates to a computer system including a plurality of storage systems and computers, and more particularly to data migration in a virtualized environment, where a storage system is virtualized.
Computers store data in the storage system. When a retention period of the data is longer than the life of the storage system, it is required to migrate the data stored in an old storage system to a new storage system before the device reaches its life. Upon the data migration, an unavailable time period is desirably as short as possible, in which the computer cannot use the storage system, and furthermore, migration is desirably conducted without any stop.
Exemplary technologies of migrating data from an old storage system to a new storage system are disclosed in JP 2004-5370 A and WO97/09676. According to JP 2004-5370 A, a computer can access data in the old storage system via the new storage system. According to WO97/09676, when data requested to be read by a computer is not present in the new storage system, the data is preferentially copied from the old storage system to the new storage system. Thus, according to JP 2004-5370 A and WO97/09676, even before the data is copied from the old storage system to the new storage system, the computer can be disconnected from the old storage system to be connected to the new storage system.